Optical scale and method for coordinate system registration

ABSTRACT

The embodiment of the present disclosure provides an optical scale comprising a support and at least three markers, wherein, the markers are fixed on the support; among all the markers, there are at least three markers whose geometric centers are not collinear; any two of the markers are different in at least one of size and shape, and any different markers do not contact each other; the material of the marker and the support enables that in a three-dimensional image obtained by three-dimensional imaging technology, the difference between a gray scale of the marker and a gray scale of the support exceeds a first predetermined value. The embodiment of the present disclosure provides a method for coordinate system registration. The embodiment of the present disclosure further provides a method for coordinate system registration by using the above optical scale.

TECHNICAL FIELD

The present disclosure relates to the technical field of automaticsurgery, and particularly relates to an optical scale and a method forcoordinate system registration.

BACKGROUND

The automated surgery (navigated surgery) means that a surgical robotautomatically performs a desired surgical operation (for example,drilling a hole in a specific position of a specific vertebra) on apatient according to a preset surgical plan. The automated surgery hasthe advantages of precise operation, no mistakes, low possibility ofinfection, no labor consumption, high efficiency, and etc.

The procedure of the automated surgery usually comprises obtaining athree-dimensional image of a patient by three-dimensional imagingtechnology, marking a surgical plan in the three-dimensional image by adoctor, and automatically performing a surgical robot on the patientaccording to the surgical plan.

Since the surgical robot and the three-dimensional image (or thethree-dimensional imaging system) have their respective coordinatesystems, it is necessary to register the coordinate systems of the twosystems (or determine the relative position relationship between the twocoordinate systems), such that the surgical robot is enabled todetermine the position of the surgical robot relative to thethree-dimensional image (that is, the position of the surgical robotrelative to the patient), so as to perform the surgery on the accuratepart of the patient body.

However, the prior art cannot accurately and quickly realize coordinatesystem registration.

SUMMARY

The embodiment of the present disclosure provides an optical scale and amethod for coordinate system registration.

In a first aspect, the embodiment of the present disclosure provides anoptical scale comprising a support and at least three markers, wherein,

the markers are fixed on the support; among all the markers, there areat least three markers whose geometric centers are not collinear; anytwo of the markers are different in at least one of size and shape, andany different markers do not contact each other;

the material of the marker and the support enables that in athree-dimensional image obtained by three-dimensional imagingtechnology, the difference between a gray scale of the marker and a grayscale of the support exceeds a first predetermined value.

In some embodiments, all of the markers have the same shape, and any twoof the markers have different sizes.

In some embodiments, all of the markers are spherical, and any two ofthe markers have different diameters.

In some embodiments, there are at most two geometric centers of themarkers in any one line.

In some embodiments, the geometric centers of all of the markers arelocated in the same plane.

In some embodiments, the support is a flat plate, and all the markersare embedded in the flat plate.

In some embodiments, the optical scale further comprising:

a connecting structure connected to the support and is used for fixingthe support on a surgical robot.

In some embodiments, the material of the marker enables that in athree-dimensional image obtained by three-dimensional imagingtechnology, the difference between a gray scale of the marker and a grayscale of human body exceeds a second predetermined value.

In some embodiments, the marker is made of steel;

the support is made of plastic.

In a second aspect, the embodiment of the present disclosure provides amethod of coordinate system registration, comprising:

fixing an optical scale on a determined position of a surgical robot,wherein the optical scale is the any one of the above optical scales;

obtaining a three-dimensional image comprising the optical scale bythree-dimensional imaging technology;

determining the position of the geometric center of each marker of theoptical scale in the three-dimensional image.

registering the coordinate system of the surgical robot and thecoordinate system of the three-dimensional image according to theposition of the optical scale relative to the surgical robot and theposition of the geometric center of each marker of the optical scale inthe three-dimensional image.

In some embodiments, the three-dimensional imaging technology is a CTimaging technology.

In some embodiments, the step that obtaining the three-dimensional imagecomprising the optical scale by three-dimensional imaging technologycomprising:

obtaining a plurality of tomographic images by CT imaging technology;

reconstructing to obtain a three-dimensional image comprising theoptical scale according to the plurality of tomographic images.

In some embodiments, the step that determining the position of thegeometric center of each marker of the optical scale in thethree-dimensional image comprising:

performing image segmentation on the three-dimensional image based onthe shape and/or size of the marker to obtain a plurality of segmentedregions;

filtering each of the segmented regions based on the gray scale of themarker, and only keeping the marking points corresponding to the marker;

extracting a plurality of characteristic regions based on the shapeand/or size of the marker, wherein each characteristic region comprisesall the marking points corresponding to one marker;

determining the shape and/or size of the virtual marker formed by themarking points in each characteristic region, and the position of thegeometric center of the virtual marker in the three-dimensional imageaccording to the marking points in each characteristic region;

determining a corresponding relationship between the virtual marker andthe marker based on the size and/or shape of the marker, with theposition of the geometric center of the virtual marker in thethree-dimensional image as the position of the geometric center of thecorresponding marker in the three-dimensional image.

In some embodiments, the step that performing image segmentation on thethree-dimensional image based on the shape and/or size of the marker toobtain a plurality of segmented regions comprising:

performing image segmentation on the three-dimensional image through aMarching Cubes algorithm based on the shape and/or size of the marker.

In the optical scale according to the embodiment of the presentdisclosure, the shape and/or size of different markers are different,that is, the size and/or shape of different markers in thethree-dimensional image are also different, so that by analyzing thesize and shape of the marker in the three-dimensional image, thecorresponding relationship between the marker in the three-dimensionalimage and the actual marker can be identified (or the markers can beidentified), and the coordinate system registration between the surgicalrobot and the three-dimensional image (or three-dimensional imagingsystem) can be realized.

Therefore, the coordinate system registration of the embodiment of thepresent disclosure can be automatedally performed, so that it does notrequire manual intervention, and is simple to be operated, efficient andaccurate. Moreover, in the embodiment of the present disclosure, byanalyzing the shape and size of the marker in the three-dimensionalimage, the corresponding relationship between the marker in thethree-dimensional image and the actual marker can be determined (or themarker can be identified), without the need to analyze the positionrelationship (arrangement) between the markers, such that the requiredcalculation process is simple, the amount of calculation is small andthe time consumption is short.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the embodiments of the disclosure, and are incorporatedin and constitute a part of this specification, and together with theembodiments of the present disclosure serve to explain the principles ofthe disclosure, and are not limited herein. The above and other featuresand advantages will become more apparent to those skilled in the art bydescribing in detail exemplary embodiments thereof with reference to theattached drawings, in which:

FIG. 1 is a schematic front view of an optical scale according to anembodiment of the present disclosure;

FIG. 2 is a schematic side view of an optical scale according to anembodiment of the present disclosure;

FIG. 3 is a schematic cross-sectional view taken along line A1B1 in FIG.1;

FIG. 4 is a schematic flow chart diagram of a method of coordinatesystem registration according to an embodiment of the presentdisclosure;

FIG. 5 is a schematic flow chart diagram of another method of coordinatesystem registration according to an embodiment of the presentdisclosure;

FIG. 6 is a schematic view of marking points and feature regions in aplane obtained in a method of coordinate system registration accordingto an embodiment of the present disclosure;

FIG. 7 is a schematic front view of another optical scale according toan embodiment of the present disclosure;

wherein the reference numbers are:

-   -   1. support; 11. opening; 2. marker; 3. connecting structure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To improve understanding of the technical solution of the embodiments ofthe present disclosure for those skilled in the of art, the opticalscale and the method for coordinate system registration according to theembodiments of the present disclosure is described in detail below withreference to the accompanying drawings.

The embodiments of the present disclosure will be described more fullyhereinafter with reference to the accompanying drawings, but theillustrated embodiments can be embodied in different forms, and shouldnot be construed as limited to the embodiments set forth herein. Rather,the purpose of providing the embodiments is to make the presentdisclosure thorough and complete, and to enable those skilled in the artto fully understand the scope of the present disclosure.

The embodiments of the present disclosure can be described withreference to plan views and/or cross-sectional views by way of idealizedschematic diagrams of the present disclosure. Accordingly, the exampleillustrations can be modified according to manufacturing techniquesand/or tolerances.

In the absence of conflict, the various embodiments and features of theembodiments of the present disclosure can be combined with each other.

The terms used in the present disclosure are used only to describeparticular embodiments and are not intended to limit the presentdisclosure. The term “and/or” as used in the present disclosurecomprises any and all combinations of one or more of the related listeditems. The singular forms “a”, “an” and “the” as used in the presentdisclosure are also intended to include the plural forms, unless thecontext clearly indicates otherwise. The terms “comprises”, “made of” asused in the present disclosure specify the presence of stated features,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Unless otherwise defined, all terms (including technical and scientificterms) used in the present disclosure have the same meaning as commonlyunderstood by one of ordinary skill in the art. It will be furtherunderstood that terms, such as those defined in commonly useddictionaries, should be interpreted as having meanings consistent withtheir meaning in the relevant art and in the background of the presentdisclosure, and will not be interpreted in an idealized or overly formalmeaning unless expressly so defined herein.

The embodiments of the present disclosure are not limited to theembodiments shown in the drawings, but include modifications ofconfigurations formed based on the manufacturing process. Thus, theregions illustrated in the drawings have schematic properties, and theshapes of the regions shown in the drawings illustrate specific shapesof regions of elements, but are not intended to be limiting.

In some related technologies, in the process of automated surgery, anoptical scale can be installed at a specific position of a surgicalrobot before actually starting surgery, and the optical scale comprisesa plurality of markers with the same shape and size, so that the markerswill also be included in the resulting three-dimensional image; in thisway, once the position of each marker in the three-dimensional image isdetermined, the relative positions of the coordinate systems of thesurgical robot and the three-dimensional image (or the three-dimensionalimaging system) can be determined by using the marker as the medium, soas to realize the coordinate system registration, so that the surgicalrobot performs the surgery according to the structure of the coordinatesystem registration.

In this case, the position of each marker in the three-dimensional imagecan be determined manually, that is, an operator (e.g., a doctor) marksthe position of each marker in the three-dimensional image in sequencebased on the experience of the doctor. However, such a method isinevitably affected by human factors (such as technical level, mistakes,etc.), and therefore, the position accuracy is difficult to be ensured,and manual intervention is required, so that the operation iscomplicated and the efficiency is low.

Alternatively, by the relative positions (arrangement) of the markers,the markers can be automatedally identified from the image and thepositions of the markers can be automatedally determined. However, thecalculation process in such a method is complicated, requiring a largeamount of calculation, and takes a long time.

In a first aspect, referring to FIGS. 1 to 3, an embodiment of thepresent disclosure provides an optical scale.

The optical scale of the embodiment of the present disclosure is used inthe field of automated surgery.

Specifically, the optical scale can be installed at a determinedposition of a surgical robot before three-dimensional imaging, such thata three-dimensional image comprising at least the optical scale can beobtained by three-dimensional imaging technology. Of course, thethree-dimensional view can also include at least a part of the surgicalrobot.

Since the optical scale is installed at a determined position of thesurgical robot (e.g. at the head of the surgical robot), the position ofthe optical scale in the coordinate system of the surgical robot can bedetermined. Meanwhile, by the method of the embodiment of the presentdisclosure, the position of the optical scale in the three-dimensionalimage can be determined, that is, the position of the optical scale inthe coordinate system of the three-dimensional image (or thethree-dimensional imaging system) is also known.

Since the position of the optical scale in the real world is unique, theposition of the optical scale in the coordinate system of the surgicalrobot and the position of the optical scale in the coordinate system ofthe three-dimensional image should be actually one position, andaccordingly, the relative position relationship between the coordinatesystem of the surgical robot and the coordinate system of thethree-dimensional image can be obtained, that is, the registration ofthe coordinate systems of the surgical robot and the three-dimensionalimage (three-dimensional imaging system) can be realized.

Specifically, the optical scale of the embodiment of the presentdisclosure comprises a support 1 and at least three markers 2, whereinthe markers 2 are fixed on the support 1; among all the markers 2, thereare at least three markers 2 whose geometric centers are not collinear;any two of the markers 2 are different in at least one of size andshape, and any different markers 2 do not contact each other.

Moreover, the material of the marker 2 and the support 1 enables that ina three-dimensional image obtained by three-dimensional imagingtechnology, the difference between the gray scale of the marker 2 andthe gray scale of the support 1 in exceeds a first predetermined value.

Referring to FIGS. 1 and 2, the optical scale comprises a support 1 anda plurality of markers 2 fixed on the support 1, that is, the support 1functions to “support” the markers 2 and to make the markers 2 have adefinite relative position (arrangement) relationship.

Moreover, the materials of the marker 2 and the support 1 are different,and usually the difference in density of which is large, so that in thethree-dimensional image obtained by three-dimensional imaging technology(e.g. CT imaging technology), the difference in the gray scales of themarker 2 and the support 1 is large (i.e. exceeds the firstpredetermined value), or in other words, the marker 2 and the support 1can be clearly distinguished in the three-dimensional image.

Specifically, the above first predetermined value can be determinedaccording to requirements and the adopted three-dimensional imagingtechnology. For example, in a three-dimensional image with a total of256 gray scales, the above first predetermined value can be 15 grayscales, 30 gray scales, 50 gray scales, or 80 gray scales, or the like.

In this case, the geometric centers of at least three markers 2 are notcollinear, i.e., the total number of markers 2 is at least three, andnot all the geometric centers of the markers 2 are located on a straightline. Since three points that are not collinear can define a plane, allmarkers 2 can define at least one plane, thereby ensuring thatregistration of two different coordinate systems is realized by aligningthe markers.

For example, if there are only three markers 2, the geometric centers ofthe three markers 2 are necessarily not on a straight line. Of course,when the number of the markers 2 is four or more, there can be asituation where there are geometric centers of three markers 2 on astraight line.

Moreover, in the embodiment of the present disclosure, any two of themarkers 2 are different in at least one of size and shape, that is, thetwo markers 2 can have the same shape and different sizes, the same sizeand different shapes, or different shapes and sizes. Therefore, any twoof the markers 2 are distinguishable by their own shape and size.

In this case, the “shape” refers to “what” shape of thethree-dimensional geometric shape of an object (e.g., spherical,ellipsoidal, cubic, tetrahedral, etc.), but without regard to theparticular “dimension” of the shape. The “size” refers to a specific“dimension” of an object.

Of course, objects of the same shape can have different sizes. Forexample, a plurality of spheres with different diameters have the same“shapes” but have different “sizes”. As such, objects with the sameshape but different sizes can become the same by scaling up/down inequal proportions.

For objects with different shapes, some of their sizes can be the same.For example, the “shapes” of the spheres and hemispheres can bedifferent, but the “sizes (diameters)” can be the same.

In this case, the different markers 2 are not in contact with eachother. That is, in the three-dimensional image, the different markers 2should be separated from each other.

Alternatively, if two objects capable of serving as markers in theoptical scale are spaced with each other, they will be the two differentmarkers 2. For example, the five black spheres in FIG. 1 are fivedifferent markers.

In contrast, if several objects capable of serving as markers arepositioned “stacked together” and in contact with each other in theoptical scale, they are one marker. For example, referring to FIG. 7, ifthere are six balls of the same size divided into three stacks, onestack having three balls, one stack having two balls, and the last stackhaving one ball, they should be considered as three markers 2, whereinone marker 2 is sphere, one marker 2 is in the form of a “string” of twoballs connected together, and the other marker 2 is in the form of astack of three balls.

In the optical scale according to the embodiment of the presentdisclosure, the shape and/or size of different markers 2 are different,that is, the size and/or shape of different markers 2 in thethree-dimensional image are also different, so that by analyzing thesize and shape of the marker 2 in the three-dimensional image, thecorresponding relationship between the marker 2 in the three-dimensionalimage and the actual marker 2 can be identified, and the coordinatesystem registration between the surgical robot and the three-dimensionalimage (or three-dimensional imaging system) can be realized.

Therefore, the coordinate system registration of the embodiment of thepresent disclosure can be automatedally performed, so that it does notrequire manual intervention, and is simple to be operated, efficient andaccurate. Moreover, in the embodiment of the present disclosure, byanalyzing the shape and size of the marker 2 in the three-dimensionalimage, the corresponding relationship between the marker 2 in thethree-dimensional image and the actual marker 2 can be determined (orthe marker can be identified), without the need to analyze the positionrelationship (arrangement) between the markers 2, such that the requiredcalculation process is simple, the amount of calculation is small andthe time consumption is short.

In some embodiments, all of the markers 2 have the same shape, and anytwo of the markers 2 have different sizes.

In the three-dimensional image, it is generally simpler to identify anobject when the shape of the object is determined than to identify anobject when the size is determined. As such, for simplicity ofoperation, all markers 2 can have the same shape, but the differentmarkers 2 can have different sizes.

In some embodiments, all of the markers 2 are spheres, and any two ofthe markers 2 have different diameters.

The sphere is a completely isotropic shape, which has no problem of“orientation”, and one sphere can be determined by only two parameters(i.e., the center and the diameter), so that it is the simplest toidentify the sphere in the three-dimensional image. Therefore, all themarkers 2 can be spheres, but have different diameters.

For example, referring to FIG. 1, the diameter of the spheres of themarkers 2, and the difference in diameter between the different spheres,can typically be in the order of millimeters. For example, the opticalscale can comprises five spherical markers 2, each marker 2 having adiameter of 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, respectively (i.e., theminimum difference in spherical diameters is 0.5 mm).

In some embodiments, there are at most two geometric centers of themarkers 2 in any one line.

The embodiments of the present disclosure do not have other absolutelimitations on the specific arrangement of the markers 2, as long asthere are three markers 2 whose geometric centers are not collinear.However, since two points can determine a straight line, considering therequirements of coordinate system registration, it is not significant tohave three or more points on a straight line, and thus, it can bespecified that there is no case where the geometric centers of the threemarkers 2 are collinear.

In some embodiments, the geometric centers of all of the markers 2 arelocated in the same plane.

In this case, the requirement of the coordinate system registration canbe satisfied as long as all the markers 2 can determine one plane.Therefore, considering the structural simplicity, it is preferable thatthe geometric centers of the markers 2 are located in the same plane.

Of course, it should be understood that the above list is only somespecific examples of the distribution of the markers 2, and is notintended to limit the embodiments of the present disclosure. Inpractical applications, the number, shape, size, and positionrelationship (arrangement) the markers 2 can be selected by thoseskilled in the art as desired.

In some embodiments, the support 1 is a flat plate, and all the markers2 are embedded in the flat plate.

Referring to FIG. 2, when all the markers 2 are located in the sameplane, the support 1 can be a flat plate, so that each marker 2 can beembedded and fixed in the flat plate, and the structure thereof issimple and the preparation thereof is convenient.

For example, referring to FIG. 3, when the markers 2 are the above fivespheres, the flat plate can have a certain thickness exceeding themaximum spherical diameter, for example, 10 mm, and the flat plate canhave openings 11 with size corresponding to the diameter of the sphereof each of the above markers 2, so that each of the markers 2 can beembedded and fixed in one opening 11.

Of course, it should be understood that the above flat plate is only onespecific example of the structure of the support 1, and that the support1 can also be other forms, for example, the support 1 can comprises aplurality of support arms, each support arm having one end fixedlyconnected to one of the markers 2 and each support arm having one endfixedly connected to a base body.

In some embodiments, the optical scale further comprises:

a connecting structure 3 connected to the support 1 and is used forfixing the support 1 on the surgical robot.

The optical scale needs to be fixed on the surgical robot, and in orderto facilitate the fixation and ensure the accuracy of the relativeposition of the fixed optical scale and the surgical robot, theconnecting structure 3 connected to a support 1 (such as a flat plate)can be provided in the optical scale.

For example, the connecting structure 3 can refer to FIGS. 1 and 2, andis a protruding portion connected to the flat plate, and has a hole atits end for inserting a screw and connecting to a surgical robot.

Of course, it is also possible to fix the optical scale at apredetermined position of the surgical robot by means of bonding or thelike, without a connecting structure.

In some embodiments, the material of the marker 2 enables that in thethree-dimensional image obtained by three-dimensional imagingtechnology, the difference between the gray scale of the marker 2 andthe gray scale of the human body exceeds a second predetermined value.

In the three-dimensional image, the human tissue of the patient isusually included as well. For this reason, the material of the marker 2should be greatly different from the human body, so that the gray scaleof the marker 2 in the three-dimensional image is greatly different fromthe gray scale of the human body (which refers to the maximum gray scalevalue that the human body tissue can reach), so that the marker 2 andthe human body can be clearly distinguished.

Specifically, the above second predetermined value can be determinedaccording to requirements and the adopted three-dimensional imagingtechnology. For example, in a three-dimensional image with a total of256 gray scales, the above first predetermined value can be 30 grayscales, 50 gray scales, 80 gray scales, 100 gray scales, or 150 grayscales, or the like.

In some embodiments, the marker 2 is made of steel; the support 1 ismade of plastic.

Specifically, the marker 2 can be made of steel, such as be a steelball; and the support 1 (including connecting structure 3) can be madeof plastic (e.g., transparent plastic), such as be a plastic flat plate.

The density of steel differs greatly from that of the human body andplastic, so that the marker 2 of steel is easily distinguished from thehuman body and the support 1. In addition, the steel and the plastic aremature materials, and which cost is low, and the preparation process ismature and simple.

Of course, the above connecting structure 3 can be formed as an integralstructure with the support 1 and be made of the same material (e.g.,plastic).

In a second aspect, referring to FIGS. 4 to 6, an embodiment of thepresent disclosure provides a method of coordinate system registration.

By using the above-mentioned optical scale, the method of the embodimentof the present disclosure is used for coordinate system registration,and more specifically for registering a coordinate system of a surgicalrobot and a coordinate system of a three-dimensional image (or athree-dimensional imaging system).

Referring to FIGS. 4 and 5, a method for coordinate system registrationaccording to an embodiment of the present disclosure comprises thefollowing steps:

S101, fixing any one of the above optical scales on a determinedposition of the surgical robot.

The above optical scale is fixed to a predetermined position of thesurgical robot, for example, the optical scale is fixed to the head ofthe surgical robot by the above connecting structure.

Of course, since the position of each marker in the optical scale isdetermined, and the optical scale is also fixed at the determinedposition of the surgical robot, the position of each marker with respectto the surgical robot is also determined, or in other words, theposition (for example, coordinate value) of each marker in thecoordinate system of the surgical robot is also determined.

S102, obtaining a three-dimensional image comprising the optical scaleby three-dimensional imaging technology.

That is, by means of three-dimensional imaging system, obtaining athree-dimensional image by imaging a space comprising the optical scaleby using three-dimensional imaging technology, and the three-dimensionalimage necessarily comprises the optical scale and can also compriseother structures such as a human body and the like.

It is obvious that the three-dimensional image (or the three-dimensionalimaging system) has its own coordinate system, i.e. each point in thethree-dimensional image has a certain coordinate value in the coordinatesystem of the three-dimensional image.

In some embodiments, the three-dimensional imaging technology is a CTimaging technology.

That is, three-dimensional imaging can be performed using CT (ComputedTomography) imaging technology.

In some embodiments, the step (S102) obtaining a three-dimensional imagecomprising an optical scale by three-dimensional imaging technologyspecifically comprises:

S1021, obtaining a plurality of tomographic images by a CT imagingtechnology.

S1022, reconstructing to obtain a three-dimensional image comprising theoptical scale according to the plurality of tomographic images.

In this case, since the CT imaging technology itself directly obtains aplurality of two-dimensional (2D) tomographic images (for example,images in DICOM format), three-dimensional reconstruction can beperformed through these 2D tomographic images (that is, the contentrepresented by each 2D image is added to a three-dimensional space) toobtain a three-dimensional image, that is, the gray scale value of eachpoint in the three-dimensional space is determined.

S103, determining the position of the geometric center of each marker ofthe optical scale in the three-dimensional image.

By analyzing the three-dimensional image, identifying the markers in thethree-dimensional image, and determining the position of the geometriccenter of each marker therein (of course, the position in the coordinatesystem of the three-dimensional image). Meanwhile, according to theshape and size of each marker, the corresponding relationship betweenthe marker in the three-dimensional image and the actual marker isdetermined, that is, the position of the geometric center of each actualmarker in the three-dimensional image is determined.

For example, assuming there are three markers A, B, C, then in thethree-dimensional image, the three markers E, F, and G and the positionof their respective geometric centers can necessarily also beidentified; since the three markers A, B, C have different shapes andsizes, by matching the shape and size of the markers E, F, and G in thethree-dimensional image with the shape and size of A, B, and C, it ispossible to determine which of the three-dimensional images E, F, Gcorresponds to each of the three-dimensional images A, B, C.

In the embodiment of the present disclosure, the correspondingrelationship of the markers can be determined by the shape and size ofthe markers themselves (i.e. the markers are identified), withoutanalyzing the relative positions (arrangement) of the markers, so thatthe calculation process is simple, the calculation amount is small, andthe time consumption is short.

S104, registering the coordinate system of the surgical robot and thecoordinate system of the three-dimensional image according to theposition of the optical scale relative to the surgical robot and theposition of the geometric center of each marker of the optical scale inthe three-dimensional image.

The position of the geometric center of each marker in the coordinatesystem of the three-dimensional image can be determined as describedabove. Also as described above, the position of each marker in thecoordinate system of the surgical robot is also known.

For the same marker, its position in the coordinate system of thethree-dimensional image and the position in the coordinate system of thesurgical robot should obviously actually be a spatial position.Therefore, it is possible to “align” the positions of the coordinatesystem of the three-dimensional image and the coordinate system of thesurgical robot that correspond to the same marker, and determine therelative position relationship (e.g., deviation of the origin positionand deviation of each coordinate axis direction) of the coordinatesystem of the three-dimensional image and the coordinate system of thesurgical robot in the case of such “alignment”, so that the conversionof the coordinates in the two coordinate systems can be realized, thatis, the “coordinate system registration” can be realized.

Obviously, since the optical scale comprises at least threenon-collinear markers, the above “alignment” manner of the coordinatesystem of the three-dimensional image and the coordinate system of thesurgical robot determined according to the embodiment of the presentdisclosure is unique, such that the accuracy of the coordinate systemregistration can be ensured.

In some embodiments, determining the position of the geometric center ofeach marker of the optical scale in the three-dimensional image (S103)comprises:

S1030, optionally, performing smooth filtering on the three-dimensionalimage.

Smooth filtering is performed on all points (including the points of themarker, the points of the support, and the points of the human body, thenoise points and the like) in the three-dimensional image to eliminatethe noise points, so as to facilitate the subsequent image segmentation.

In this case, generally, the more times of smooth filtering, the moreconducive to image segmentation.

However, the smooth filtering also has a blurring effect, so that if thetimes of smooth filtering are too much, it will lead to too muchblurring of the three-dimensional image. It is found that the times ofsmooth filtering is more appropriate around 15 times.

In this case, the specific way of the smooth filtering can be meanfiltering, median filtering, Gaussian filtering, etc., and will not bedescribed in detail herein.

S1031, performing image segmentation on the three-dimensional imagebased on the shape and/or size of the marker to obtain a plurality ofsegmented regions.

That is, segmentation parameters are set according to the shape and size(both known) of the marker, and a three-dimensional image is segmentedinto a plurality of “small three-dimensional images”, that is, aplurality of segmented regions is obtained.

In some embodiments, the image segmentation the three-dimensional imagebased on the shape and/or size of the marker to obtain a plurality ofsegmented regions (S1031) specifically comprises:

S10311, performing image segmentation on the three-dimensional imagethrough a Marching Cubes algorithm based on the shape and/or size of themarker.

That is, the image segmentation can be specifically performed using amarching cubes (MC) algorithm.

Specifically, the marching cubes algorithm is a “minicube” that segmentsthe three-dimensional image into a plurality of specific sizes (the sizebeing determined according to the shape and size of the marker). Eachminicube has either no overlap with the marker, or overlaps with themarker, and by analyzing the gray scale of 8 vertices of each minicube(i.e., whether the vertices are in the marker or not), the overlapsituation of each minicube with the marker (including whether and how itoverlaps) can be determined, and the intersection of the iso-surface(i.e., the surface) of the marker with the 12 sides of the minicube canbe determined.

S1032, filtering each segmented region based on the gray scale of themarker, and only keeping the marking point corresponding to the marker.

Filtering all points in each segmented region (small cube),specifically, filtering out points which do not belong to the markers(such as points of a human body or points of a support) according to thegray scale of the markers, so that the rest points are points (markingpoints) corresponding to the markers.

It should be understood that for the segmented regions not overlappingwith the marker, there are no more points in the segmented regions afterthe current filtering, and for the segmented regions overlapping withthe marker, all of the rest of the segmented regions after the currentfiltering are the marking points corresponding to the marker. Therefore,this step is equivalent to obtaining a “point cloud” of all markers inthe three-dimensional image.

S1033, extracting a plurality of characteristic regions based on theshape and/or size of the marker, wherein each characteristic regioncomprises all the marking points corresponding to one marker.

That is, extraction parameters are set according to the shape and size(both known) of the marker, and three-dimensional regions withpredetermined shapes but different sizes are attempted to extract thethree-dimensional image, and finally, a plurality of feature regionshaving a predetermined shape and different sizes are extracted. In eachof the above feature regions, all the marking points corresponding toone marker are included, and the marking points corresponding to theother markers are not included, and the feature region is preferably thesmallest region that can “load” the marker.

For example, when the markers are the above five spheres with differentdiameters, the feature region can be a cube with a side length matchingthe diameter of the above sphere. Referring to FIG. 6, in one plane ofthe three-dimensional image, the marking points corresponding to theabove markers can be a plurality of points within a circle in thefigure, and the boundary of the feature region can be the dotted line inthe figure.

S1034, determining the shape and/or size of the virtual marker formed bythe marking points in the characteristic region, and the position of thegeometric center of the virtual marker in the three-dimensional imageaccording to the marking points in each characteristic region.

In each feature region, all marking points (or point clouds) belong toone marker, so that a marker (virtual marker) can be determined by thesepoints, and the position of the geometric center of the virtual marker,as well as the size and position of the virtual marker, can bedetermined.

For example, when the markers are the above five spheres with differentdiameters, the coordinate value of the geometric center (i.e., thespherical center) of each marker can be determined by the followingformula:

Center_x=(Σ_(i) ^(n) x _(i))/n;

Center_y=(Σ_(i) ^(n) y _(i))/n;

Center_z=(Σ₁ ^(n) z)/n;

Wherein, Center_x, Center_y and Center_z are coordinate values of thecenter of sphere on the X axis, the Y axis and the Z axis respectively,and obviously, the X axis, the Y axis and the Z axis are three axeswhich are mutually vertical; x_(i), y_(i) and z_(i) are the coordinatesof the “i”-th marking point on the X axis, Y axis and Z axis,respectively, and n is the total number of marking points in eachfeature region (or the total number of marking points corresponding tothe marker).

Further, the diameter of each sphere can be determined by the sidelength of the feature region corresponding to the sphere.

Of course, it is also feasible if the position of the virtual marker andits geometric center are determined by other means. For example, themarking points in each feature region can be “fitted” to a virtualobject (virtual marker) having a predetermined shape (e.g., a sphere) bya least square method or the like, and the size and the position of thegeometric center of the virtual marker can be determined.

S1035, determining a corresponding relationship between the virtualmarker and the marker based on the size and/or shape of the marker, withthe position of the geometric center of the virtual marker in thethree-dimensional image as the position of the geometric center of thecorresponding marker in the three-dimensional image.

As described above, since the shapes and sizes of the different markersare different from each other, it is possible to determine each virtualmarker corresponds to which actual marker based on the shapes and sizesof the virtual markers obtained from the three-dimensional image, and itis possible to determine of the geometric center of each of the actualmarkers should correspond to which geometric center of the virtualmarker.

For example, when the markers are the above five spheres with differentdiameters, the positions of the centers of the spheres (virtual markers)can be output in an order of sorting the diameters (for example, sortingfrom small to large), and respectively corresponds to the actual sphere(marker), that is, the position of the geometric center of each markerin the three-dimensional image is determined and used in the subsequentstep of coordinate system alignment.

The present disclosure has disclosed example embodiments, and althoughspecific terms are employed, they are used and should be interpreted ina generic and descriptive sense only and not for purposes of limitation.In some examples, it would be apparent to those skilled in the art thatfeatures, characteristics and/or elements described in connection with aparticular embodiment can be used alone or in combination with features,characteristics and/or elements described in connection with otherembodiments, unless expressly stated otherwise. Therefore, it will beunderstood by those skilled in the art that various changes in form anddetails can be made therein without departing from the scope of thedisclosure as set forth in the appended claims.

1. An optical scale comprising a support and at least three markers,wherein, the markers are fixed on the support; among all the markers,there are at least three markers whose geometric centers are notcollinear; any two of the markers are different in at least one of sizeand shape, and any different markers do not contact each other; thematerial of the marker and the support enables that in athree-dimensional image obtained by three-dimensional imagingtechnology, the difference between a gray scale of the marker and a grayscale of the support exceeds a first predetermined value.
 2. The opticalscale according to claim 1, wherein, all of the markers have the sameshape, and any two of the markers have different sizes.
 3. The opticalscale according to claim 2, wherein, all of the markers are spherical,and any two of the markers have different diameters.
 4. The opticalscale according to claim 1, wherein, there are at most two geometriccenters of the markers in any one line.
 5. The optical scale accordingto claim 1, wherein, the geometric centers of all of the markers arelocated in the same plane.
 6. The optical scale according to claim 5,wherein, the support is a flat plate, and all the markers are embeddedin the flat plate.
 7. The optical scale according to claim 1, wherein,further comprising: a connecting structure connected to the support andis used for fixing the support on a surgical robot.
 8. The optical scaleaccording to claim 1, wherein, the material of the marker enables thatin a three-dimensional image obtained by three-dimensional imagingtechnology, the difference between a gray scale of the marker and a grayscale of human body exceeds a second predetermined value.
 9. The opticalscale according to claim 1, wherein, the marker is made of steel; andthe support is made of plastic.
 10. A method of coordinate systemregistration, comprising: fixing an optical scale on a determinedposition of a surgical robot, wherein the optical scale is the opticalscale according to claim 1; obtaining a three-dimensional imagecomprising the optical scale by three-dimensional imaging technology;determining the position of the geometric center of each marker of theoptical scale in the three-dimensional image; registering the coordinatesystem of the surgical robot and the coordinate system of thethree-dimensional image according to the position of the optical scalerelative to the surgical robot and the position of the geometric centerof each marker of the optical scale in the three-dimensional image. 11.The method of claim 10, wherein, the three-dimensional imagingtechnology is a CT imaging technology.
 12. The method of claim 11,wherein, the step that obtaining a three-dimensional image comprisingthe optical scale by three-dimensional imaging technology comprising:obtaining a plurality of tomographic images by CT imaging technology;reconstructing to obtain a three-dimensional image comprising theoptical scale according to the plurality of tomographic images.
 13. Themethod of claim 10, wherein, the step that determining the position ofthe geometric center of each marker of the optical scale in thethree-dimensional image comprising: performing image segmentation on thethree-dimensional image based on the shape and/or size of the marker toobtain a plurality of segmented regions; filtering each of the segmentedregions based on the gray scale of the marker, and only keeping themarking points corresponding to the marker; extracting a plurality ofcharacteristic regions based on the shape and/or size of the marker,wherein each characteristic region comprises all the marking pointscorresponding to one marker; determining the shape and/or size of thevirtual marker formed by the marking points in each characteristicregion, and the position of the geometric center of the virtual markerin the three-dimensional image according to the marking points in eachcharacteristic region; determining a corresponding relationship betweenthe virtual marker and the marker based on the size and/or shape of themarker, with the position of the geometric center of the virtual markerin the three-dimensional image as the position of the geometric centerof the corresponding marker in the three-dimensional image.
 14. Themethod of claim 13, wherein, the step that performing image segmentationon the three-dimensional image based on the shape and/or size of themarker to obtain a plurality of segmented regions comprising: performingimage segmentation on the three-dimensional image through a MarchingCubes algorithm based on the shape and/or size of the marker.